Process for sulfurized olefinic product

ABSTRACT

A process for preparing, in high yield, a sulfurized olefinic product for use in lubricating oil compositions having a low chlorine content, a sulfur content of from about 40 to about 50 weight percent and a viscosity at 100° C. of less than about 20 cSt.

This application is a division of application Ser. No. 940,615, filed Sep. 4, 1992, now abandoned, which in turn is a continuation-in-part of application Ser. No. 739,092 filed Aug. 1, 1991, now abandoned.

BACKGROUND

This invention relates to a process for preparing, in high yield, a sulfurized OLEFINIC product for use in lubricating oil compositions having a low chlorine content, a sulfur content of from about 40 to about 50 weight percent and a viscosity at 100° C. of less than about 20 cSt.

A number of methods for the preparation of sulfurized olefin products that can be used as additives for lubricants are described in the prior art.

Myers, U.S. Pat. No. 3,471,404, describes a process for the preparation of stable non-corrosive organosulfur compounds which are substantially monomeric. The monomeric organosulfur compounds are prepared by reacting the adduct formed from the reaction between an olefin and sulfur monochloride with an alkali metal sulfide and free sulfur in the presence of an alcohol or an alcohol-water solvent under reflux conditions. Subsequently, the polysulfurized olefin is contacted with an inorganic base in a water solution to remove chlorine to less than about 0.5 weight percent.

Papay et al., U.S. Pat. No. 4,204,969, describe a method for the preparation of olefin polysulfides comprising the steps of reacting sulfur monochloride with a C₃ -C₆ aliphatic mono-olefin in the presence of a promoter consisting of a lower alcohol (preferably isopropanol) in order to form an adduct. The adduct is then reacted with sulfur or sodium sulfide in a ratio of 0.1 to 0.4 gram-atom of sulfur per mole of sodium sulfide in an aqueous alcoholic medium at a temperature ranging from 50° C. to the reflux temperature. The mixture is held at reflux for 2-8 hours to assure complete reaction. After the reflux period, the alcohol is distilled from the mixture and the product recovered by conventional methods.

In addition, Borne et al., U.S. Pat. No. 4,645,610, disclose a method for the preparation of olefin polysulfides comprising contacting an addition product produced by the reaction of at least one aliphatic monoolefin containing 2 to 5 carbon atoms and sulfur monochloride or dichloride with a hydrocarbyl halide and at least one sulfur compound selected from sulfides, hydrosulfides and polysulfides of alkali metals, ammonium or alkaline-earth metals and usually elemental sulfur in an aqueous or aqueous alcoholic medium at certain reaction conditions so as to obtain products whose kinematic viscosity is not too high. When an alcoholic reaction medium is used, the preferred alcohol is isopropanol. If necessary, the product is treated with an inorganic base subsequent to the formation reaction. The product thus obtained has a viscosity of about 4 to 20 mm² /s and a halogen content of less than 1 weight percent.

Zaweski et al., U.S. Pat. No. 4,954,274, describe a process for obtaining sulfurized olefinic compounds which are soluble in both mineral and synthetic oils of lubrication viscosity. The first stage of the process is conducted by adding an olefin to sulfur monochloride in the presence of minor amounts of an active Lewis acid to form an adduct. The adduct from the first stage of the process is then reacted with sodium sulfide and sulfur in an aqueous alkanol reaction medium (preferably isopropanol) at a temperature of about 50° C. up to reflux. After reaction of the adduct with sodium sulfide and sulfur, the product is recovered by conventional methods such as removing alkanol, water washing, vacuum drying and filtering.

DeGonia et al , U.S. Pat. No. 4,966,720, relate to sulfurized olefins useful as EP additives in lubrication oils and to a two-stage process for their preparation. In the second stage of the process a sulfur monochloride/aliphatic monoolefin adduct is reacted in a basic, aqueous alcoholic solution containing sodium sulfide at a temperature of from about 50° C. up to reflux to form the sulfurized olefin. When using the preferred alcohol, isopropanol either alone or mixed with other alkanols such as ter-butanol, and a reaction temperature of preferably 75° to 85° C., the resulting sulfurized polyalkylene product of DeGonia, et al. typically contains more than 5000 ppm chlorine.

While the foregoing methods provide sulfurized olefin products which are useful in lubricant mixtures, the chlorine content of the products of the foregoing processes is generally above about 1000 ppm and often above 5000 ppm. There remains a need for a sulfurized olefin product having a substantially lower chlorine content yet containing the amount of sulfur desired and having acceptable copper corrosion and viscosity properties.

THE INVENTION

It has now been discovered that a sulfurized olefinic product, having a chlorine content of less than about 5000 ppm, preferably less than about 2000 ppm, and most preferably less than about 1000 ppm and containing more than about 30 weight percent sulfur, preferably more than 35 weight percent sulfur and most preferably more than 40 weight percent sulfur, can be prepared by contacting an adduct of a sulfur halide and an olefin with a sulfur source in an alkaline aqueous medium comprising water and a lower alkanol, which alkanol has a boiling point of greater than about 85° C.; maintaining the so contacted adduct at a temperature and for a period of time which are sufficient to form a mixture having an aqueous phase containing alcohol and water and an organic phase containing a sulfurized olefinic product; and heating the organic phase for a period of time and at a temperature and pressure sufficient to form, in high yield, the sulfurized olefinic product having a chlorine content of less than about 1000 ppm.

Heretofore, sulfurized olefinic product has been made by a process which, although effective in obtaining a product with the desired sulfur content, usually had a chlorine content of 4000 ppm or more. It has been discovered surprisingly, and quite unexpectedly, that utilizing a mixture containing an alcohol having a boiling point above a particular temperature for contacting the adduct of a sulfur halide and an olefin with a sulfur source has made a substantial difference in the amount of chlorine in the recovered sulfurized olefinic product. Hence, the alcohol or mixture of alcohols thus selected to form the adduct contacting mixture is a key feature of this invention.

By high yield is meant greater than about 50 percent yield based on theoretical. For example, if about 500 grams of adduct are charged to a reaction vessel, more than about 250 grams of sulfurized olefinic product are thus obtained.

The process of this invention also provides a sulfurized olefinic product having an acceptable viscosity. Oftentimes, when the product is post-treated so as to reduce the chlorine content, the viscosity of the thus treated product increases. It is highly desirable that the product have a viscosity at 100° C. of less than about 20 cSt, preferably less than about 15 cSt, and most preferably in a range of from about 2 cSt to about 10 cSt. These and other advantages will be evident from the ensuing description.

In another embodiment, this invention provides a sulfurized olefinic lubrication oil additive which imparts extreme pressure properties, having a chlorine content of less than about 1000 ppm and made by a process comprising contacting an adduct of a sulfur halide and an olefin with a sulfur source in an alkaline aqueous medium comprising water and a lower alkanol, the alkanol having a boiling point greater than 85° C.; maintaining the so contacted adduct at a temperature and for a period of time which are sufficient to form an aqueous phase containing alcohol and water and an organic phase containing a sulfurized olefinic product; and heating the organic phase for a period of time and at a pressure sufficient to form, in high yield, the sulfurized olefinic product having a chlorine content of less than about 1000 ppm.

In yet another embodiment, this invention provides a process for preparing a sulfurized olefin having a chlorine content of less than about 4,000 ppm, the process comprising contacting an adduct of a sulfur halide and an olefin with a sulfur source in an alkaline alcoholic aqueous medium; maintaining the so-contacted reaction product at a temperature and for a period of time which are sufficient to form an aqueous phase containing alcohol and an organic phase containing a sulfurized olefin polymer; and heating the organic phase for a period of time and at a pressure sufficient to form the sulfurized olefinic having a chlorine content of less than about 4,000 ppm.

In accordance with the invention, the starting olefins are the monoethylenically unsaturated aliphatic hydrocarbons referred to as aliphatic monoolefins containing 3 to about 6 carbon atoms. These include 1-butene, 2-butene, isobutene, 1-pentene, 2-pentene, 2-methyl-1-butene, 3-methyl-1-butene, 2-methyl-2-butene, 1-hexene, 2-hexene, 3-hexene, 2-methyl-1-pentene, 2-methyl-2-pentene, 2-ethyl-2-butene and the like including mixtures thereof.

Preferably, the olefins are branched chain olefins such as isobutene, 2-methyl-1-butene, 1-methyl-2-butene, 2-methyl-2-pentene and the like. More preferably, the ethylenically double bond adjoins a tertiary carbon atom such as isobutylene, the most preferred olefin.

The adduct of sulfur halide and olefin is preferably formed by adding olefin to a sulfur monochloride. The olefin can be added as a gas or liquid.. Preferably, the olefin is added beneath the surface of the sulfur monochloride as a gas.

In practice, the olefin is added until the reaction with the sulfur monochloride stops as indicated by loss of exotherm. An amount of about 0.45-2.0 gram moles of olefin per each 0.3-0.75 gram moles of sulfur monochloride usually suffices. A preferred amount is about 1.7-2.2 grams moles of olefin per gram mole of sulfur monochloride.

Preferably, the adduct of olefin and sulfur monochloride is formed without adding an alkanol promoter, but the use of an alkanol promoter may be used if so desired. When used, the alkanol promoter is typically a lower alkanol having from about 1 to about 4 carbon atoms such as methanol, ethanol, n-propanol, isopropanol, isobutanol, tert-butanol and the like. The most preferred promoter is methanol.

The lower alkanol promoter, when desirably used, can be added to the sulfur monochloride initially, added to the reaction mixture continuously or periodically during the course of olefin addition or the alkanol can be mixed with the olefin and added together with the olefin. The preferred modes of addition are to either add the entire amount initially and then add the olefin or to concurrently add both alkanol and olefin.

The amount of alkanol promoter is desirably in a range of from about 0.001 to about 0.3 gram moles for each 0.3-0.75 gram mole of sulfur monochloride.

The adduct forming step can be conducted at any temperature high enough to cause the reaction to proceed, but not so high as to cause decomposition of the reactants or products. A useful range is about -30° to 100° C. A more preferred range is about -20° to 75° C. and a most preferred range is about 0° to 20° C. for lower viscosity products and 20° to 60° C. for higher viscosity products. The lower viscosity products tend to be more soluble than the higher viscosity products in some lubricants and hence there is a need for a process which is flexible enough to produce either high or low viscosity products.

The adduct forming step should be conducted for a time sufficient to complete the reaction between the sulfur monochloride and olefin. This is usually limited by heat removal. Olefin feed rate is preferably controlled to hold the temperature within the desired range. When the sulfur monochloride has been consumed, the temperature will drop. External heat may be added to continue the reaction for a further time, but this does not appear to be necessary. The overall time required to complete the reaction depends upon the scale of the processing and can vary from a few minutes up to 12 hours or more. The time is not critical.

During the adduct forming step, HCl gas is evolved so means should be provided to scrub the vent gas from the reactor to remove HCl prior to releasing it from the atmosphere.

After forming the adduct, the adduct is contacted with a sulfur source in an alkaline aqueous medium comprising a lower alkanol having a boiling point of greater than about 85° C. and water. The sulfur source may be elemental sulfur, NaHS, Na₂ S, Ag₂ S, Bi₂ S₃, CuS, Cu₂ S, H₂ S, MnS, SnS, and the like. Preferably, the sulfur source is provided by elemental sulfur or NaHS and most preferably by a mixture of elemental sulfur and NaHS. Optionally, if hydrogen sulfide is available, it can be adsorbed in aqueous NaOH to form a solution of sodium sulfide and/or sodium hydrosulfide, depending upon the amount of hydrogen sulfide adsorbed.

The amount of total sulfur in the alkaline aqueous medium is critical in obtaining the desired sulfurized olefinic product having a sulfur content of more than about 30 weight percent. Hence the alkaline aqueous medium should contain more than about 1 mole of total sulfur per mole of adduct, more preferably more than about 1.4 moles of total sulfur per mole of adduct and most preferably in the range of from about 1.5 to about 1.7 moles of total sulfur per mole of adduct. In a particularly preferred embodiment, the ratio of the gram atoms of elemental sulfur to moles of NaHS is in the range of from about 0.01:1 to about 0.25:1, preferably from about 0.04:1 to about 0.2:1 and most preferably from about 0.08:1 to about 0.1:1. With regard to the amount of adduct charged to the reaction vessel, the most preferred ratio of NaHS to adduct is in the range of from about 1.3:1 to about 1.5:1; and the most preferred ratio of S to adduct is in the range of from about 0.05:1 to about 0.3:1.

When NaHS and elemental sulfur are used as the sulfur source, the aqueous medium further comprises a basic solution, typically a metal hydroxide or alkaline earth metal hydroxide. In a particularly preferred embodiment, the alkaline aqueous medium comprises more than about 0.7 moles of NaOH per mole of adduct, preferably more than about 0.8 moles of NaOH per mole of adduct, and most preferably in the range of from about 0.9 to about 1.0 moles of NaOH per mole of adduct.

A key feature of the invention is the use of an alkanol having a boiling point of greater than about 85° C. in the mixture for preparing the polysulfurized polyalkylene product. Preferably, the alcohol is a lower alcohol containing 1-4 carbon atoms such as n-propanol, n-butanol, isobutanol, tert-butanol and the like including mixtures thereof. The preferred alkanol is n-propanol either alone or mixed with other alkanols such as tert-butanol.

The amount of alkanol can vary over a wide range. A useful range is about 0.2-0.8 parts by weight per each part by weight of adduct. A more preferred range is about 0.4-0.65 parts by weight per each part of adduct.

The alcohol employed in the invention can either be a virgin alcohol or a mixture of virgin alcohols and recycle alcohols obtained as a distillate from a previous sulfurization reaction. In a preferred embodiment, the alcohol is a recycle alcohol containing from about 85-100 weight percent n-propanol and from about 0-15 weight percent tert-butanol. It not critical to the invention that the alcohol used be a mixture of n-propanol and t-butanol, however, when a mixture of alcohols is used, it is critical that there be substantially more n-propanol than t-butanol. It is particularly preferred to utilize a recycle n-propanol containing about 10 weight percent t-butanol.

In addition to the alkanol and sulfur source, the alkaline medium also contains an amount of water sufficient to form the alkaline aqueous medium. Typically the total amount of water in the alkaline medium is, on a weight basis, substantially equal to the amount of adduct added to the aqueous medium. The water may be added with the sulfur source, the metal hydroxide or the alkaline earth metal hydroxide, the alkanol, or any combination of two or all three of the foregoing. Optionally, free water may be added to the alkaline medium taking into account the amount of water entering the alkaline medium from any of the foregoing sources.

The sequence of addition of the sulfur source, alkanol, and water to the alkaline aqueous medium is not critical to the invention. Hence, each of the foregoing may be added in any order or in any combination. The adduct, however, is preferably added after forming the alkaline aqueous medium containing the sulfur source, alkanol and water. It is, of course, understood that additional water may be added to the alkaline aqueous medium after addition of the adduct in order to obtain the desired amount of water in the aqueous medium.

It may be desirable to add an anti-foaming agent to the aqueous medium prior to, during, or after the addition of the adduct. When it is desirable to add such an antifoam agent the antifoam agent thus selected should be compatible with the aqueous medium and product formed. Hence, any of the well known antifoam agents may be used. It has been found that antifoam B (Dow Corning Company) is particularly suitable for use as an antifoam agent in the process of this invention.

Prior to addition of the adduct, the alkaline aqueous medium is typically heated to above about 50° C., preferably above 60° C., most preferably about 70° C. When the aqueous medium reaches the desired temperature, the adduct is added with agitation over an extended period of time. The agitation rate for the medium is not critical to the invention as long as the agitation rate is sufficient to maintain the components of the medium and adduct in suspension so that there is sufficient contact between the adduct and the sulfur source. Depending on the batch size, the period of time for adduct addition may be up to about 10 hours or more. It is particularly preferred, however, to add the adduct at a constant rate over a period of about 2-4 hours. The rate of addition of the adduct is not critical as long as the adduct is added to the medium over a period of at least about 2 hours. During the addition of the adduct, the temperature of the medium will rise from about 70° C. to reflux. The rate of addition of the adduct is dependent on the ability of the equipment to maintain the temperature at reflux during the adduct addition.

Subsequent to the addition of the adduct to the medium, the resulting mixture is maintained at an elevated temperature for a period of time (cook period) sufficient to form an organic phase containing the sulfurized olefinic product with a minor amount of alkanol, water and solids; and an aqueous phase containing the alkanol and water with a minor amount of organic product and solids. It is particularly preferred that the resulting mixture be maintained at reflux for more than about 1.5 hours to assure adequate contact between the adduct and the sulfur source. The period of time the mixture is maintained at the elevated temperature is most preferably about 2-4 hours or longer.

After the cook period, the temperature of the mixture is increased to effectively strip the alkanol from the reaction mass. The temperature required to strip the alcohol from the mixture is dependent on the particular alcohol mixture and the pressure utilized in the stripping operation. It is highly desirable that the alcohol be stripped under vacuum at a temperature in the range of from about 85° C. to about 100° C. and most preferably about 90° to 95° C. During the stripping operation a subatmospheric pressure may be applied and the stripping operation continued until the pressure reaches about 20-23 inches Hg vacuum. Once a vacuum of about 23 inches of mercury is obtained, the vacuum source is cut off and an amount of water is added with agitation to the stripped mixture. Upon termination of the agitation, a separate aqueous phase thus forms. The amount of water added to form the aqueous phase is in the range of from about 60 to about 100 wt. % of the weight of adduct initially charged.

Subsequent to the water addition and agitation for about 10 to 30 minutes, the agitation is terminated and the reaction medium is allowed to settle in order to form two phases, an aqueous phase containing alcohol and water and an organic phase containing the sulfurized olefinic polymer. Once the organic and aqueous phases are formed, the aqueous phase is separated from the organic phase by decantation or other mechanical means, and the organic phase is heated to remove residual water. Typically the organic phase is heated to a temperature in the range of from about 100° to about 120° C. and under a reduced pressure of about 20-28 inches of Hg for about 10 minutes to about an hour. The product is then recovered by conventional methods such as filtration, centrifugation, and the like.

The exact structure of the sulfurized olefinic product is not known, but it is believed to be a polymeric product containing alkylene sulfur bridged structures.

The following examples are presented to illustrate the invention and are not to be considered as limiting any aspect thereof.

EXAMPLE 1 Addition of Sulfur Monochloride to Isobutylene

Liquid sulfur monochloride, (135.0 grams), was charged into a suitable reaction flask equipped with a stirrer, thermometer, a condenser maintained at 5° C. and a sub-surface gas sparger. Thereafter, gaseous isobutylene was bubbled into the reaction flask below the surface of the sulfur monochloride liquid while stirring to bring the temperature up to about 55° C. A total of 187.9 grams of isobutylene was added. The adduct thus formed was a clear amber oil.

Example 2 is presented for comparative purposes and illustrates the use of an alkanol having a boiling point of less than 85° C.

EXAMPLE 2 Preparation of Sulfurized Olefinic Product

A reaction flask is charged with 108.4 grams of water, 3.6 grams of elemental sulfur, 1/2 a dropper of antifoam B, 368.0 grams isopropanol, 150.2 grams of 50 weight percent aqueous sodium hydroxide, and 393.3 grams of 35 weight percent aqueous NaHS. The mixture is stirred and heated under nitrogen to 70° C. at which time 513 grams of the isobutylene-sulfur monochloride adduct of Example 1 is added subsurface over a 4 hour period while maintaining the reaction mass at reflux (76°-84° C.). Heat is continued at reflux for two hours and then the alcohol is stripped out by heating up to 90° C. at atmospheric pressure. Following the atmospheric strip, the pressure is reduced to 23 inches of Hg while allowing the flask to cool to about 72° C. to complete the removal of the alcohol and most of the water. To the resulting product is added 300 grams of water which, after stirring for 10 minutes is allowed to settle for 5 minutes. The lower aqueous brine layer is separated and the organic layer is vacuum stripped (28 inches Hg) at 100° C. After filtering the stripped organic layer through a bed of diatomaceous earth, a clear yellow oil is obtained. Analysis of product made by the foregoing procedure typically has a viscosity in the range of 7.0 to 8.0 cSt at 100° C., a sulfur content of about 44-47 weight percent, chlorine content of about 0.7-0.75 weight percent and a copper corrosion test weight loss (CCT) of about 35-85 milligrams per 100 mL of sample.

Examples 3 and 4 illustrate the process of this invention utilizing an alkanol having a boiling point higher than 85° C.

EXAMPLE 3 Preparation of Sulfurized Olefinic Product Having Low Cl₂

A reaction flask is charged with 173.7 grams of water, 8.4 grams of elemental sulfur, 1/2 a dropper of antifoam B, 261.0 grams of reagent grade n-propanol, 29.0 grams of reagent grade t-butanol, 143.4 grams of 50 weight percent aqueous sodium hydroxide, and 409.3 grams of 35 weight percent aqueous NaHS. The mixture is stirred at 700 rpm and heated under nitrogen to 70° C. at which time 503.7 grams of the isobutylene-sulfur monochloride adduct of Example 1 is added subsurface over a 2 hour period while maintaining the reaction mass at reflux (92°-94° C.). Heat is continued at reflux for four hours and then the alcohol is stripped out by heating up to 100° C. at atmospheric pressure. Following the atmospheric strip, the pressure is reduced to 23 inches of Hg while allowing the flask to cool to about 72° C. to complete the removal of the alcohol and most of the water. To the resulting product is added 300 grams of water which, after stirring for 10 minutes is allowed to settle for 5 minutes. The lower aqueous brine layer is separated and the organic layer is vacuum stripped (28 inches Hg) at 100° C. After filtering the stripped organic layer through a bed of diatomaceous earth, a clear yellow oil weighing 315.8 grams was obtained. Analysis of a product made by the foregoing procedure had a viscosity of 7.8 cSt at 100° C., a sulfur content of about 45.8 weight percent, chlorine content of 500 ppm and a copper corrosion test result (CCT) of about 45.1 milligrams per 100 mL of sample.

EXAMPLE 4 Preparation of Sulfurized Olefinic Product Having Low Cl₂

Sulfurized olefinic polymer product was made by the procedure of Example 3. After filtering the stripped organic layer through a bed of diatomaceous earth, a clear reddish-yellow oil weighing 318.3 grams was obtained. Analysis of a product made by the foregoing procedure has a viscosity of 8.3 cSt at 100° C., a sulfur content of about 45.8 weight percent, chlorine content of 700 ppm and a CCT of about 42.9 milligrams per 100 mL of sample.

In another set of comparative reactions, a sulfurized olefinic product was prepared according to the procedure in U.S. Pat. No. 4,966,720. In Example 5, the alkanol was isopropanol containing 8.62 weight percent t-butanol based on the total weight of alkanol. In Example 6, the alkanol was n-propanol containing 8.62 weight percent t-butanol based on the total weight of alkanol.

EXAMPLE 5 Preparation of Sulfurized Isobutylene Using Isopropanol

A reaction flask equipped with an agitator was charged with 49.4 grams of water (2.74 moles) which was heated to about 20° C., 8.5 grams of elemental sulfur (0.26 moles), 242.2 grams of reagent grade isopropanol, 22.8 grams of reagent grade t-butanol, 143.2 grams of 50 weight percent aqueous sodium hydroxide (71.6 moles NaOH), and 437 grams of 34 weight percent aqueous NaHS (2.64 moles of NaHS). About 1/2 drop of defoamer was also included in the initial charge. The mixture was stirred at 700 rpm and heated under nitrogen to 50° C. at which time 500 grams of the isobutylene-sulfur monochloride adduct of Example 1 having a mole ratio of isobutylene to sulfur monochloride of 1.85 was added subsurface over a 2 and 1/2 hour period with the reaction mixture being allowed to exotherm to about 70° C. and then the reaction mass was maintained at about 78° C. at atmospheric pressure until the adduct addition was complete. The reaction mass was then heated to alcohol reflux temperature (82° C.) and refluxed for about 3 hours. The H₂ S evolved was removed by caustic scrubbing. After reflux, the alcohol was stripped at atmospheric pressure by heating up to 90° C. Following the atmospheric strip, the pressure was reduced to 23 inches of Hg to complete the removal of the alcohol and most of the water. To the resulting product was added 625 grams of water with stirring and heating to 60° to 65° C. in order to wash the organic layer after which agitation and heating was stopped and the mixture separated into an organic phase and a brine layer. The lower aqueous brine layer was separated and the organic layer and was vacuum stripped of water containing residual sulfur at 100 mm Hg and 100°-100° C. After filtering the stripped organic layer through a bed of diatomaceous earth, a clear yellow oil was obtained. Product made by the foregoing procedure had a viscosity of 6.88 cSt at 100° C., a sulfur content of about 43.7 weight percent, chlorine content of 2300 ppm and a CCT of about 37.5 milligrams per 100 mL of sample.

EXAMPLE 6 Preparation of Sulfurized Isobutlyene Using n-propanol

The procedure of Example 5 was repeated utilizing the same amount of reactants and solvent but with 242.2 grams of reagent grade n-propanol, 22.8 grams of reagent grade t-butanol. In this run, the reaction mixture was refluxed at 90° C. for 3 hours after the adduct addition was complete. Product made by the foregoing procedure had a viscosity of 9.07 cSt at 100° C., a sulfur content of about 46.2 weight percent, chlorine content of 800 ppm and a CCT of about 40.7 milligrams per 100 mL of sample.

As Examples 5 and 6 illustrate, that the use of an alkanol having a boiling point of greater than 85° C., i.e. n-propanol, as compared to an alkanol having a boiling point of less than 85° C., i.e. isopropanol, results in more than a 65 percent decrease in the amount of chlorine remaining in the sulfurized isobutylene product.

For the copper corrosion test (CCT) weight loss analysis a weighed copper strip is immersed in the sulfurized olefinic product of this invention for three hours at 121° C. The corrosion scale is removed using 10 percent sodium cyanide solution and the copper strip is re-weighed to determine the weight loss.

The sulfurized olefins of the invention are especially useful as extreme pressure additives for lubricating oil formulations, especially in gear applications. The base oils can be of mineral or synthetic origin. Synthetic oils include, in particular, olefin oligomers such as decene trimer, tetramer and pentamer made by oligomerizing 1-decene using a BF₃ catalyst. Useful olefin oligomers can be made using other catalysts such as the aluminum alkyl Ziegler catalyst. Likewise, other olefins can be used such as C₆₋₁₄ 1-olefins.

In this application, the sulfurized olefin products of the invention are added in amounts sufficient to improve the extreme pressure property of the lubricant. Amounts of from 0.2 to 10.0 weight percent based on the total weight of the additized lubricant are usually sufficient.

These additives can be used in combination with other conventional additives which perform various functions. Examples of such other additives are corrosion inhibitors for ferrous and non-ferrous metals such as tetrapropenyl succinic acid and bis-(2,5-alkyldithio)-1,3,4-thiadiazoles as well as antiwear addictives such as alkyl or aryl phosphonates, phosphites, thiophosphates, dithiophosphates, and phosphoric acids. Also zinc dialkyl or diaryl dithiophosphate, chlorinated hydrocarbons, sulfurized fatty esters and amines can be added. 

What is claimed is:
 1. A process for preparing, in high yield, a sulfurized olefinic product having a chlorine content of less than about 2000 ppm and a sulfur content of more than about 30 weight percent comprising:a) contacting an adduct of a sulfur halide and an olefin with a sulfur source in an alkaline aqueous medium comprising water and a lower alkanol at a temperature of from about 20° to 100° C. said alkanol having a boiling point of greater than about 85° C. to thereby form a mixture having an aqueous phase containing alcohol and water and an organic phase containing a sulfurized olefinic product; and b) heating the organic phase to form, in high yield, the sulfurized olefinic product having a chlorine content of less than about 2000 ppm.
 2. The process of claim 1 wherein the temperature of the mixture formed in step a) is in the range of from about 90° C. to reflux.
 3. The process of claim 1 wherein the sulfur source is S, or NaHS, or S and NaHS.
 4. The process of claim 1 wherein the lower alkanol is n-propanol, or a mixture of n-propanol and t-butanol.
 5. The process of claim 3 wherein the molar ratio of NaHS to adduct is in the range of from about 1.3:1 to about 1.5:1.
 6. The process oft claim 3 wherein the molar ratio of S to adduct is in the range of from about 0.05:1 to about 0.3:1.
 7. The process of claim 3 wherein the molar ratio of NaHS to adduct is in the range of from about 1.3:1 to about 1.5:1 and the ratio of S to adduct is in the range of from about 0.05:1 to about 0.3:1.
 8. The process of claim 7 wherein the lower alkanol is n-propanol or a mixture of n-propanol and t-butanol, and wherein the weight ratio of alcohol to adduct is in the range of from about 0.5:1 to about 0.65:1.
 9. The process of claim 8 wherein the alcohol is comprised of about 90 weight percent n-propanol and about 10 weight percent t-butanol.
 10. The process of claim 9 wherein the sulfur halide is sulfur monochloride and the olefin is isobutylene.
 11. The process of claim 1 wherein the weight ratio of lower alkanol to adduct is in the range of from about 0.5:1 to about 0.65:1.
 12. The process of claim 1 wherein the lower alkanol is comprised of about 90 weight percent n-propanol and about 10 weight percent t-butanol.
 13. The process of claim 1 wherein the sulfur halide is sulfur monochloride.
 14. The process of claim 1 wherein the olefin is isobutylene. 